Page 26 - Patrick Moreau - Marine Knots How to Tie 40 Essential Knots

Round Turn and Two Half Hitches

The value of the round turn cannot be overstated.

While it is quite simple, it allows you to maintain the tension on a rope by
increasing arm force. And if the tension is too great, there is nothing wrong with
doing a second round turn.
This gesture has somewhat fallen out of favor with pleasure boaters, but it is
the first step of the most iconic sailing knot: a round turn and two half hitches.
An exceptional hitching knot, it is one of the few that can be tied and untied
under great tension.